System and method for active filtering in a telecommunications network

ABSTRACT

A filtering device ( 50 ) for active filtering at a customer premises includes an input interface that receives telephone signals and digital data signals communicated from a central office ( 14 ) using a telephone line ( 12 ). The filtering device ( 50 ) further includes an active low-pass filter ( 60 ) that receives the telephone signals, the digital data signals, and electrical power from a power source. The active low-pass filter ( 60 ) attenuates the digital data signals and passes the telephone signals using the electrical power. The filtering device ( 50 ) also includes an output interface that receives the telephone signals from the active low-pass filter ( 60 ) and communicates the telephone signals to a telephone ( 42 ).

TECHNICAL FIELD OF THE INVENTION

This invention relates generally to the field of telecommunications, andmore particularly to a system and method for active filtering in atelecommunications network.

BACKGROUND OF THE INVENTION

Many computing applications require the digital transmission of data toand from customer premises using the analog telephone system.Conventional modem technology is one such method. This technologytransmits digital data over the telephone lines that connect customerpremises with the local telephone company's central office or anintermediate device such as a digital loop carrier (DLC). Thesetelephone lines are typically twisted-pair copper wire and may bereferred to as the “local loop.” Conventional modem technology transmitsthe data in analog form over the local loop using the frequency bandallocated for voice transmissions. However, the frequency range of thevoice band, typically below 4 kHz, limits the speed at which a givenvolume of the data can be transmitted.

Digital subscriber line (DSL) technology, on the other hand, canapportion the transmission of signals over telephone lines into a voicechannel and a digital data channel. For example, the voice channel mayinclude signals below 4 kHz while the digital data channel may includesignals above 25 kHz. Using this digital data channel, DSL provides amethod of increasing the bandwidth of the existing telephone networkinfrastructure. Furthermore, DSL technology allows conventional plainold telephone service (POTS) devices that use the voice channel and DSLdevices using the digital data channel to communicate simultaneouslyover the local loop. To accomplish this task, splitters or filters maybe used to separate the two channels. Typically, a splitter or filter isplaced at the central office, the customer premises, or both.

One filtering technique that may be used at the customer premises is adistributed filter architecture. In a distributed filter architecture, alow-pass filter is coupled between a customer premises wiring interface(such as an RJ-11 jack) and each telephone. For example, each telephone,facsimile machine, and other conventional telephony device may becoupled to a low-pass filter which is coupled to the customer premisestelephone wiring. Each low-pass filter allows signals in the voicechannel to travel to and from the conventional devices, while filteringout traffic and noise associated with devices using the digital datachannel.

SUMMARY OF THE INVENTION

According to the present invention, disadvantages and problemsassociated with previous techniques for filtering in atelecommunications network have been substantially reduced oreliminated.

According to one embodiment of the present invention, a filtering devicefor active filtering at a customer premises includes an input interfacethat receives telephone signals and digital data signals communicatedfrom a central office using a telephone line. The filtering devicefurther includes an active low-pass filter that receives the telephonesignals, the digital data signals, and electrical power from a powersource. The active low-pass filter attenuates the digital data signalsand passes the telephone signals using the electrical power. Thefiltering device also includes an output interface that receives thetelephone signals from the active low-pass filter and communicates thetelephone signals to a telephone.

The system and method of the present invention provide a number ofimportant technical advantages. The present invention provides afiltering device for use in conjunction with DSL service at a customerpremises that attenuates the high frequency digital data signalsassociated with the DSL service and prevents them from interfering withthe telephones located at the customer premises. The filtering devicemay help prevent disruption of telephone service due to faults in theDSL equipment, such as a DSL modem. Furthermore, the filtering devicemay prevent noise associated with the digital data signals from undulyinterfering with the analog telephone signals used by POTS telephones orthe digital telephone signals used by ISDN telephones, while preventinghigher frequency interference or noise associated with the telephonesfrom unduly interfering with the digital data signals.

These functions are performed while reducing or eliminating losses intelephone signals that have been characteristic of previous passivefiltering devices, particularly losses created when installing more thanthree to five of these passive filtering devices at a customer premises.Unlike passive filtering devices, a virtually unlimited number offiltering devices constructed according to the present invention may beimplemented at a customer premises without creating unacceptable losses.Furthermore, unlike previous passive filtering devices, numerousfiltering devices constructed according to the present invention may beimplemented without creating interference between the telephone signals(POTS, ISDN, or otherwise) and the digital data signals (which may causeloss of data in the digital data signals). In addition, the presentinvention provides filtering devices that provide high order filteringwithout unduly degrading performance. To obtain similar order filteringusing passive filtering devices, a relatively large number of cascadedfilters are required, resulting in undesirable signal loss andinterference. Other technical advantages are readily apparent to thoseskilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

To provide a more complete understanding of the present invention andfurther features and advantages thereof, reference is now made to thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 illustrates an exemplary digital subscriber line (DSL) systemusing a splitter at a customer premise;

FIG. 2 illustrates an alternative DSL system without a splitter at thecustomer premises;

FIG. 3 illustrates an exemplary filtering device at a customer premise;

FIG. 4 illustrates an alternative filtering device using an externalpower supply;

FIG. 5 illustrates another alternative filtering device using thecustomer premises telephone wiring to obtain electrical power;

FIG. 6 illustrates yet another alternative filtering device using thecurrent from the telephone line to obtain electrical power; and

FIG. 7 illustrates exemplary packaging of the filtering device of FIG.5.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an exemplary digital subscriber line (DSL) system 10a. DSL technologies allow existing twisted-pair telephone lines, usedfor plain old telephone service (POTS), or other types of communicationlines to communicate both telephone signals (either analog or digital)and digital data signals between network equipment at a central officeand equipment at a customer premises. System 10 a may support asymmetricDSL (ADSL), ISDN DSL (IDSL), symmetric DSL (SDSL), high-data-rate DSL(HDSL), rate-adaptive DSL (RADSL), very-high-data-rate DSL (VDSL) or anyother suitable “xDSL” technology or other method of transmitting digitaldata over analog telephone lines, digital ISDN lines, or any otherappropriate communication lines.

System 10 a includes a customer premises 12, a central office 14, a datanetwork 16, and a telephone network 18. In one embodiment, a pair ofsplitters 20 and 22 (at central office 14 and customer premises 12,respectively) are used to receive signals transmitted using atwisted-pair or other suitable telephone line 24 from customer premises12 and central office 14, respectively. Telephone line 24 may alsoinclude integrated services digital network (ISDN) lines, unshieldedtwisted-pair (UTP) lines, or any other appropriate communication lines.The signals generally include, without limitation, a telephone signal ina lower frequency band and a digital data signal in a higher frequencyband. In a particular embodiment, the lower frequency band includes aband of frequencies below approximately 4 kHz and the higher frequencyband includes a band of frequencies above approximately 25 kHz (thefrequency bands typically associated with analog POTS telephone signalsand ADSL data signals, respectively). In another embodiment, the lowerfrequency telephone signals are digital ISDN telephone signals havingfrequencies below approximately 80 kHz.

At central office 14, splitter 20 receives an input signal communicatedfrom splitter 22 using telephone line 24. As described above, the inputsignal generally includes a telephone signal in a lower frequency bandand a data signal in a higher frequency band. Splitter 20 processes theinput signal and separates the data signal from the telephone signal. Inone embodiment, splitter 20 communicates the separated data signal to aDSL modem 26 or a modem bank (such as a DSL access multiplexer (DSLAM))using link 28. DSL modem 26 receives the data signal from splitter 20and communicates corresponding data to data network 16 using link 30.Data network 16 may include any suitable group of one more linkedcomputers, such as a local area network (LAN), a wide area network(WAN), the Internet, or any other suitable network for communicatingdata signals. Splitter 20 communicates the telephone signal to telephonenetwork 18 using link 32. Telephone network 18 may include any suitablegroup of one or more linked telephone switches, such as a publicswitched telephone network (PSTN), a private switched telephone network,or any other suitable network for communicating telephone signals. Links28, 30, and 32 may be any suitable wireless, wireline, or othercommunication links and may each be associated with one or moreintermediate components.

Splitter 22 at customer premises 12 receives an input signalcommunicated from splitter 20 using telephone line 24. Again, the inputsignal generally includes a telephone signal in a lower frequency bandand a data signal in a higher frequency band. Splitter 22 processes theinput signal and separates the data signal from the telephone signal.Splitter 22 communicates the separated data signal to a DSL modem 34using link 36. DSL modem 26 receives the data signal and communicatescorresponding data to computer 38 using link 40. Computer 38 may be apersonal computer, a workstation, a personal digital assistant, or anyother suitable processing or communication device. Although DSL modem 34is shown as external from computer 38, DSL modem 34 may be integral toor separate from computer 38 according to particular needs. splitter 22communicates the separated telephone signal to telephones 42 using links44. Telephones 42 may include one or more POTS telephones, ISDNtelephones, facsimile machines, analog voice-band modems, or any othersuitable devices. Links 36, 40, and 44 may be any suitable wireless,wireline, or other communication links and may each be associated withone or more intermediate components. In particular, links 44 may includethe customer premises telephone wiring.

FIG. 2 illustrates DSL system 10 b using an alternative configurationwithout splitter 22. Such a configuration may be implemented whensplitterless DSL (for example, G.Lite or DSL Lite) is used. In thisembodiment, the telephone and data signals are communicated fromsplitter 20 to DSL modem 34 without passing through a splitter atcustomer premises 12. DSL modem 34 includes components thatdifferentiate the data signals from the telephone signals. System 10 balso includes active filtering devices 50 constructed according to thepresent invention that are located between each telephone 42 and thelinks 44 (such as customer premises telephone wiring 44) coupling thetelephones 42 to telephone line 24. For example, a filtering device 50may be located between each telephone 42 and an RJ-11 telephone jackproviding an interface to customer premises telephone wiring 44. In oneembodiment, filtering devices 50 are wired in parallel to one another.

Filtering devices 50 are implemented so as to allow the lower-frequencytelephone signals to pass, but to filter out any higher-frequency datasignals. For example, filtering devices 50 may each include a low-passfilter circuit that filters out signals over 4 kHz. Filtering devices 50help to prevent disruption of telephone service due to faults in the DSLequipment, such as DSL modem 34. Furthermore, filtering devices 50 mayprevent noise associated with the data signals from unduly interferingwith the operation of telephones 42, while preventing higher frequencyinterference or noise associated with telephones 42 from undulyinterfering with the data signals. Filtering devices 50 may also be usedin a similar manner in system 10 a to supplement the filtering performedby splitter 22. Filtering devices 50 perform these functions whilereducing or eliminating losses and interference associated with previousfiltering devices.

FIG. 3 illustrates customer premises 12 and an exemplary filteringdevice 50 a in further detail. Although customer premises 12 isillustrated without splitter 22, it should be understood that filteringdevice 50 a may be used as described below either with or withoutsplitter 22. Filtering device 50 a is coupled between telephone 42 andan RJ-11 jack 52 or any other appropriate jack used to couple telephone42 to customer premises telephone wiring 44. Jack 52 typically includeselectrical connections to at least four wires, which typically runbetween multiple jacks 52 in customer premises 12 to form customerpremises telephone wiring 44. Two of the wires for which jack 52includes a connection, wires 54, are coupled to telephone line 24 (whichitself includes two corresponding wires). Wires 54, and the twocorresponding wires of telephone line 24, are typically referred to asthe tip and ring wires and carry the telephone and data signals betweencentral office 14 and telephone 42 or DSL modem 34. The other two wiresincluded in customer premises telephone wiring 44 need not be used inconjunction with the embodiment illustrated in FIG. 3, but will bedescribed in further detail below.

As described above, filtering device 50 a is used to filter outhigher-frequency data signals and to pass lower-frequency telephonesignals. In one embodiment, filtering device 50 a performs this functionusing an active low-pass filter 60 that passes telephone signals belowapproximately 4 kHz and attenuates data signals above approximately 25kHz, although any appropriate filtering may be performed. Low-passfilter 60 may filter signals sent to telephone 42 from central office 14and signals sent from telephone 42 to central office 14. Low-pass filter60 is an active filter that uses electrical power in its operation andmay be constructed according to techniques known to those skilled in theart. Low-pass filter 60 may use any components appropriate for an activelow-pass filter including, but not limited to, operational amplifiers,resistors, and capacitors.

Unlike passive low-pass filters presently used for telephone signalfiltering, active low-pass filters 60 may be used in customer premises12 with minimal degradation of the telephone signals. Passive filtersuse components, such as inductors, that create loss in the telephonesignal (such as a reduction in the amplitude of the signal). If customerpremises 12 includes numerous telephones 42 and each telephone 42 has acorresponding passive low-pass filter, unacceptable losses may becreated. Therefore, certain passive low-pass filter vendors specify thata maximum of three to five filters should be used in a customer premise.In addition, to obtain higher-order filtering and precise attenuation ofthe data signals, the number of components in a passive low-pass filtermust typically be increased. This increased number of components alsocauses an increased amount of loss associated with each passive filter.Furthermore, numerous passive filters also create interference betweenthe telephone signals and the data signals (which may cause loss of datain the data signals).

The use of active low-pass filter 60 in filtering device 50 reduces oreliminates these losses and interference. For example, low-pass filter60 may use operational amplifiers that are gained so as to compensatefor losses created by other components of filter 60. In addition, activelow-pass filter 60 may be used to achieve a relatively high order filter(for example, eighth or higher order filtering) that provides theattenuation of the high frequency signals desired to prevent undueinterference with the operation of telephones 42 and DSL modem 34. Inaddition, multiple active low-pass filters 60 may be connected inparallel to customer premises telephone wiring 44 (one filter 60 coupledto each telephone 42) with minimal losses to the telephone signals sentto and from telephones 42 and with minimal interference between thetelephone signals and the data signals.

One advantage of passive filters is that they do not require power to besupplied from an external source. Active low-pass filter 60, however,does use electrical power. Therefore, the present invention includesappropriate techniques for supplying power to low-pass filter 60. In theembodiment illustrated in FIG. 3, filtering device 50 a includes one ormore batteries 62 that supply power to low-pass filter 60. Anyappropriate type and number of batteries 62 may be used to meet thepower requirements of low-pass filter 60, and batteries 62 may becoupled to low-pass filter 60 in any appropriate manner. Furthermore,batteries 62 may be configured to operate only when the associatedtelephone 42 is operating, so that battery power may be conserved.Batteries 62 may also include rechargeable batteries that may berecharged periodically using the electrical service provided at customerpremises 12 or any other appropriate power source.

FIG. 4 illustrates an alternative filtering device 50 b using a powersupply 64. Power supply 64 may be coupled to an electrical outlet 66 orother external source of power using wires 68. Wires 68 may include apositive supply wire, a negative supply wire, and a ground wire.Electrical outlet 66 may include, but is not limited to, an existingoutlet that is a part of the electrical wiring of customer premises 12,and power supply 64 may include, but is not limited to, one or moretransformers that may step down the typical 120V alternating currentsupplied by electrical outlet 66. Alternatively, additional electricalwiring may be installed at customer premises 12 to provide electricalcurrent to power supply 64 or directly to low-pass filter 60. Thiswiring may include, but is not limited to, wiring 69 coupled to DSLmodem 34 or other appropriate DSL customer premises equipment (CPE) soas to allow the DSL CPE to provide power to filtering device 50 b.Although wiring 69 is illustrated as being coupled to power supply 64,wiring may be directly coupled to active low-pass filter 60, ifappropriate.

FIG. 5 illustrates another alternative filtering device 50 c usingcustomer premises telephone wiring 44 to obtain electrical power. Asdescribed above, telephone wiring 44 typically includes four wires towhich a connection is provided at jacks 52. Two of these wires are tipand ring wires 54 used to communicate the telephone and data signals toand from central office 14. The other two wires 70 may be used toprovide electrical power to one or more operational amplifiers or otherappropriate components that are included in active low-pass filter 60.Pump operational amplifiers may be implemented that use a positive powersupply to create a negative power supply, so that only two wires areconnected to the operational amplifier: a positive supply wire and aground wire. Therefore, one of wires 70 may be used as a positive supplywire and the other wire may be used as a ground wire.

In the illustrated embodiment, DSL modem 34 or any other DSL CPE mayinclude one or more components that provide electrical power asdescribed above to one or more operational amplifiers or othercomponents in filtering device 50 c using wires 70. Since wires 70 aretypically included in customer premises telephone wiring 44, noadditional wiring is typically required to provide this power from theDSL CPE. In addition, any other device coupled to customer premisestelephone wiring 44 may provide this power to filtering device 50 c.Furthermore, an RJ-11 jack typically has connections for six wires,although only four wires are used in a typical customer premisestelephone wiring 44. However, if telephone wiring 44 includes at leastone additional wire 72, wire 72 could be used along with wires 70 toprovide the three-wire electrical power supply described above withreference to FIG. 4. In this case, power could be supplied to filteringdevice 50 c using a positive supply wire, a negative supply wire, and aground wire without the use of additional wiring 68 (described abovewith reference to FIG. 4) coupling filtering device 50 c to anelectrical power source. For example, wires 70 and 72 may be coupled toa DSL CPE in a similar manner as described above to provide power tofiltering device 50 c using customer premises telephone wiring 44.

FIG. 6 illustrates yet another alternative filtering device 50 d using acurrent supplied on telephone line 24 to obtain electrical power. Inconjunction with the operation of telephones 42, a current may besupplied over telephone line 24 by central office 14 or any otherappropriate source. For example, central office 14 may provide a currentof approximately 60-70 mA over telephone line 24 when a telephone 42goes off-hook. This current may be referred to as a loop current.Filtering device 50 d includes a power supply 73 that transforms theloop current to create a voltage appropriate for active low-pass filter60.

FIG. 7 illustrates exemplary packaging of filtering device 50 c. Sincefiltering device 50 c does not require a battery or external powersupply, filtering device 50 c may be contained in a relatively smallpackage. In addition, a set of wires 54 and 70 (and optionally wire 72)may be coupled to an input and an output of filtering device 50 c, andeach set of wires 54 and 70 may be terminated with an RJ-11 plug 74 orother appropriate connector for facilitating connection of filteringdevice 50 c between customer premises telephone wiring 44 and telephone42. The combination of filtering device 50 c, wires 54 and 70, and plugs74 may be referred to as a dungle. Alternatively, filtering device 50 cmay include an RJ-11 jack in place of each set of wires 54 and 70 andplug 74 to allow a user to provide wires 54 and 70 having a lengthselected by the user. Wires 54 and 70 provided by the user would beterminated with a plug 74 for insertion into one of the jacks associatedwith filtering device 50 c. In either case, filtering device 50 cincludes RJ-11 input and output interfaces (either a plug or a jack)that facilitate the coupling of filtering device 50 c to wires 54 and70.

Filtering devices 50 a, 50 b, and 50 d may also be implemented asillustrated in FIG. 7 with the addition of either a battery 62, anelectrical power supply 64 and accompanying wires 68, or a power supply73, respectively. Battery 62 or a power supply 64 or 73 may be coupledto an electrical interface providing power to the appropriatecomponent(s) of active low-pass filter 60. Furthermore, filters 50 a-50d may be implemented in any other appropriate manner, includingincorporation into a telephone 42, a splitter 22 (if applicable), or aDSL router coupled between central office 14 and telephones 42.

Although the present invention has been described with severalembodiments, numerous changes, substitutions, variations, alterations,and modifications may be suggested to one skilled in the art, and it isintended that the invention encompass all such changes, substitutions,variations, alterations, and modifications as fall within the spirit andscope of the appended claims.

What is claimed is:
 1. A filtering device for active filtering at acustomer premises, comprising: an input interface operable to receivetelephone signals and digital data signals communicated from a centraloffice using a telephone line; an active low-pass filter operable toreceive the telephone signals and the digital data signals from theinput interface, and to receive electrical power from one or morecomponents of digital subscriber line (DSL) customer premises equipment(CPE), the active low-pass filter further operable to attenuate thedigital data signals and pass the telephone signals using the electricalpower; and an output interface operable to receive the telephone signalsfrom the active low-pass filter and communicate the telephone signals toa telephone; wherein the input interface comprises an RJ-11 interfaceincluding electrical connections for a first tip wire, a first ringwire, and for at least two additional wires operable to provideelectrical power from the one or more components of the DSL CPE to theactive low-pass filter via the RJ-11 interface.
 2. The filtering deviceof claim 1, wherein: the telephone signals comprise analog signalshaving a frequency below approximately 4 kHz; and the digital datasignals comprise DSL signals having a frequency above approximately 25kHz.
 3. The filtering device of claim 1, wherein: the RJ-11 interface iscoupled to customer premises telephone wiring comprising: the first tipwire and the first ring wire; and the at least two additional wires; andthe RJ-11 interface is operable to receive the electrical power from theone or more components of the DSL CPE using the customer premisestelephone wiring.
 4. The filtering device of claim 1 wherein: the activelow-pass filter comprises an operational amplifier; and the at least twoadditional wires operable to provide electrical power comprise apositive supply wire and a ground wire electrically coupled to theoperational amplifier.
 5. The filtering device of claim 1, wherein theinput interface comprises: a telephone line interface comprising theelectrical connections for the first tip wire and the first ring wire;and an electrical power interface comprising the electrical connectionsfor the at least two additional wires.
 6. The filtering device of claim5, wherein: the telephone line interface is coupled to customer premisestelephone wiring comprising the first tip wire and the first ring wire,the first tip and first ring wires coupled to the telephone line; andthe electrical power interface is electrically coupled to the one ormore components of DSL CPE operable to provide electrical power.
 7. Thefiltering device of claim 5, wherein: the active low-pass filtercomprises an operational amplifier; and the electrical power interfaceis coupled to the operational amplifier.
 8. The filtering device ofclaim 1, wherein the output interface comprises an RJ-11 interfaceincluding electrical connections for a second tip wire and a second ringwire for coupling the output interface to the telephone.
 9. Thefiltering device of claim 8, wherein: the output interface is operableto receive output signals from the telephone comprising telephonesignals and noise signals having a frequency higher than the frequencyof the telephone signals, the output interface further operable tocommunicate the output signals to the active low-pass filter; and theactive low-pass filter is operable to receive the output signals fromthe output interface and the electrical power from the input interface,the active low-pass filter further operable to attenuate the noisesignals and pass the telephone signals using the electrical power. 10.The filtering device of claim 9, wherein the input interface is operableto receive the telephone signals from the active low-pass filter andcommunicate the telephone signals to the telephone line.
 11. A methodfor active filtering at a customer premises, comprising: at an inputinterface, receiving telephone signals and digital data signalscommunicated from a central office using a telephone line; communicatingthe telephone signals and digital data signals from the input interfaceto an active low-pass filter; at the active low-pass filter, receivingthe telephone signals and digital data signals from the input interfaceand receiving electrical power from one or more components of digitalsubscriber line (DSL) customer premises equipment (CPE); using theactive low-pass filter, attenuating the digital data signals and passingthe telephone signals using the electrical power; and communicating thetelephone signals from the active low-pass filter to an output interfacecoupled to a telephone; wherein the input interface comprises an RJ-11interface including electrical connections for a tip wire, a ring wire,and for at least two additional wires operable to provide electricalpower from the one or more components of the DSL CPE to the activelow-pass filter via the RJ-11 interface.
 12. The method of claim 11,wherein: the telephone signals comprise analog signals having afrequency below approximately 4 kHz; and the digital data signalscomprise DSL signals having a frequency above approximately 25 kHz. 13.The method of claim 11, wherein: the RJ-11 interface is coupled tocustomer premises telephone wiring including the tip wire, the ringwire, and the at least two additional wires; and the RJ-11 interfacereceives electrical power from the one or more components of the DSL CPEusing the customer premises telephone wiring.
 14. The method of claim11, wherein receiving telephone signals and digital data signals at theinput interface comprises receiving the signals using customer premisestelephone wiring comprising the tip line and the ring line coupled tothe telephone line.
 15. The method of claim 11, further comprising: atthe output interface, receiving output signals from the telephonecomprising telephone signals and noise signals having a frequency higherthan the frequency of the telephone signals; communicating the outputsignals to the active low-pass filter; and using the active low-passfilter, attenuating the noise signals and passing the telephone signalsusing the electrical power.
 16. The method of claim 15, furthercomprising communicating the telephone signals to the telephone line.17. A filtering device for active filtering at a customer premises,comprising: a first interface means for receiving telephone signals anddigital data signals communicated from a central office using atelephone line; a filter means for receiving the telephone signals andthe digital data signals from the first interface, and for receivingelectrical power from one or more components of digital subscriber line(DSL) customer premises equipment (CPE) and for attenuating the digitaldata signals and passing the telephone signals using the electricalpower; and a second interface means for receiving the telephone signalsfrom the filter means and for communicating the telephone signals to atelephone; wherein the first interface means comprises an RJ-11interface including electrical connections for a first tip wire, a firstring wire, and for at least two additional wires operable to provideelectrical power from the one or more components of the DSL CPE to theactive low-pass filter via the RJ-11 interface.
 18. The filtering deviceof claim 17, wherein: the telephone signals comprise analog signalshaving a frequency below approximately 4 kHz; and the digital datasignals comprise DSL signals having a frequency above approximately 25kHz.
 19. The filtering device of claim 17, wherein: the RJ-11 interfaceis coupled to customer premises telephone wiring comprising: the firsttip wire and the first ring wire; and the at least two additional wires;and the RJ-11 interface is operable to receive the electrical power fromthe one or more components of the DSL CPE using the customer premisestelephone wiring.
 20. The filtering device of claim 17, wherein: thefilter means comprises an operational amplifier; and the at least twoadditional wires operable to provide electrical power comprise apositive supply wire and a ground wire electrically coupled to theoperational amplifier.
 21. The filtering device of claim 17, wherein thefirst interface means comprises: a telephone line interface comprisingthe electrical connections for the first tip wire and the first ringwire; and an electrical power interface comprising the electricalconnections for the at least two additional wires.
 22. The filteringdevice of claim 21, wherein: the telephone line interface is coupled tocustomer premises telephone wiring comprising the first tip wire and thefirst ring wire, the first tip and first ring wires coupled to thetelephone line; and the electrical power interface is electricallycoupled to the one or more components of DSL CPE operable to provideelectrical power.
 23. The filtering device of claim 21, wherein: thefilter means comprises an operational amplifier; and the electricalpower interface is coupled to the operational amplifier.
 24. Thefiltering device of claim 17, wherein the second interface meanscomprises an RJ-11 interface including electrical connections for asecond tip wire and a second ring wire for coupling the output interfaceto the telephone.
 25. The filtering device of claim 24, wherein: thesecond interface means is operable to receive output signals from thetelephone comprising telephone signals and noise signals having afrequency higher than the frequency of the telephone signals, the secondinterface means further operable to communicate the output signals tothe filter means; and the filter means is operable to receive the outputsignals from the second interface means and the electrical power fromthe first interface means, the filter means further operable toattenuate the noise signals and pass the telephone signals using theelectrical power.
 26. The filtering device of claim 25, wherein thefirst interface means is operable to receive the telephone signals fromthe filter means and communicate the telephone signals to the telephoneline.